A computer may operate a vehicle in an autonomous mode, a semi-autonomous mode, or a non-autonomous mode. In the autonomous mode each of vehicle propulsion, braking, and steering may be controlled by the computer. In the semi-autonomous mode the computer may control one or two of vehicles propulsion, braking, and steering. In the non-autonomous mode, a human operator may control the vehicle propulsion, braking, and steering. Accordingly, the operator may, or may not, need to interact with certain user input systems, e.g., a steering wheel assembly.